Pivoting coupling system for a large dihedral empennage to the tail fuselage of an aircraft

ABSTRACT

Pivoting coupling system of a large dihedral empennage to the tail fuselage of an aircraft, in which the empennage ( 1 ) comprises a right lateral box (la) and a left lateral box ( 1   b ) arranged at a large dihedral angle in the tail fuselage ( 6 ) of the aircraft, characterised in that it comprises a horizontal central box ( 1   c ) joining the lateral boxes ( 1   a,    1   b ), and which comprises a rear spar ( 11 ); and means of linkage ( 2, 3, 4 ) for horizontally linking the central box ( 1   c ) to a frame structure ( 7, 8, 9 ) of the tail fuselage ( 6 ) of the aircraft, which allow the empennage ( 1 ) to rotate vertically about a horizontal linkage shaft ( 5 ) between a negative maximum angle of incidence (−θ 1 ) and a positive maximum angle of incidence (+θ 2 ) in response to the actuation of actuator means which are connected to the empennage ( 1 ) and to a structural element of the fuselage of the aircraft.

TECHNICAL FIELD OF THE INVENTION

This invention belongs to the field of aeronautics and particularly tothe sector of couplings between V-shaped tails, also known as largedihedral empennages, and structural elements of the fuselage ofaircraft.

PRIOR ART OF THE INVENTION

Large dihedral empennages have for decades been known in combat aircraftsuch as the F-117A Nighthawk, and in light aircraft such as the BeechD35 Bonanza, for example. Nevertheless, in large passenger transportaircraft, this type of empennage has not been used, due in part to thefact that it behaves differently from empennages with separatehorizontal and vertical stabilisers, since the loads which this type oftail imply for the structure of the fuselage displayed difficulties whenit came to designing a coupling that was reliable, safe and ofacceptable weight.

DESCRIPTION OF THE INVENTION

The aim of the present invention is to overcome the difficultiesmentioned above by means of a pivoting coupling system for a largedihedral empennage to the tail fuselage of an aircraft, in which theempennage comprises a right lateral box and a left lateral box arrangedat a large dihedral angle in the tail fuselage of the aircraft, saidsystem comprising a horizontal central box joining the lateral boxes andwhich comprises a rear spar; and

means of linkage for horizontally linking the central box to a framestructure of the tail fuselage of the aircraft., which allow theempennage to rotate vertically about a horizontal linkage shaft betweena negative maximum angle of incidence −θ₁ (corresponding to a positionin an ascent manoeuvre of the aircraft) and a positive maximum angle ofincidence +θ₂ (corresponding to a position in a descent manoeuvre of theaircraft) in response to the actuation of actuator means which areconnected to the empennage and to a structural element of the fuselageof the aircraft.

This arrangement of elements permits the efficient coupling of the largedihedral empennage which acts as the elevator in the tail fuselage ofthe aircraft.

In an embodiment of the invention, the frame structure includes a closedframe and the means of linkage include a first linked fitting providedin the proximity of the right box. In this embodiment, the first linkedfitting comprises a first rotary fitting provided in the frame structureand linked by means of a first bolt to a complementary first rotaryfitting provided in the rear spar of the empennage. The second linkedfitting is provided in the proximity of said left box and comprises asecond rotary fitting provided in the frame structure and linked bymeans of a second bolt to a complementary second rotary fitting providedin the rear spar of the empennage. Each of the complementary rotaryfittings in turn includes at least one complementary opening alignedwith at least one opening in one of the rotary fittings and acomplementary opening in at least one of the complementary rotaryfittings, in order to form a space in which the bolt is housed. At leastone lateral load linked fitting is in turn provided in this embodimentin order to prevent lateral displacements of the empennage, which isprovided in the central box between the linked fittings and whichcomprises a lateral load fitting provided in the frame structure linkedto at least one complementary lateral load fitting which is provided inthe rear spar of the empennage. These lateral load fittings are linkedtogether such that they permit the empennage to rotate on the saidhorizontal shaft.

The closed frame structure preferably comprises an upper section, acentral section and a lower section, the means of linkage being providedin the central section of the closed frame.

In accordance with the invention, each of the rotary fittings caninclude a first fitting element with at least one lower anchoring pointand at least one upper anchoring point and at least two lugs between theanchoring points. Each lug has an opening for the bolt to pass through.

In a preferred embodiment of the invention, each rotary fittingcomprises a central fitting element in the form of an elongated bodywith two ends and arranged in a first side of the closed frame, alongwith a first counter-fitting element and a second counter-fittingelement arranged on the opposite side of the closed frame. In thisembodiment, the central fitting element comprises a first lateral wallwith a free edge from which emerge a first lug with a first opening, afirst lateral wing arranged between the first end of the central fittingelement and the first lug, and a second lateral wing arranged betweenthe second end of the central fitting element and the first lug. Thesecond lateral wall also has a free edge from which emerge a second lugwith a second opening, a third lateral wing arranged between the firstend of the central fitting element and the second lug, and a fourthlateral wing arranged between the second end of the central fittingelement and the second lug. The lateral walls are joined by a centralwall. Each of the lugs is coplanar with the lateral wall from which itemerges. The lateral wings in turn extend the respective lateral wallsin the opposite direction to said central wall. The firstcounter-fitting element comprises a first plate (13a) with a first endand a second end between which an edge is defined from which extend athird lug with a third opening coplanar with the first plate, a fifthlateral wing laterally emerging from said edge between said first endand the third lug, and a sixth lateral wing laterally emerging from saidedge between said second end and the third lug. The secondcounter-fitting element has a configuration which is the mirror image ofthe first counter-fitting element, and comprises a second plate with afirst end and a second end, between which an edge is defined from whichextend a fourth lug with a fourth opening coplanar with the second platewith a fourth opening, a seventh lateral wing laterally emerging fromsaid edge between said first end and the fourth lug, and an eighthlateral wing laterally emerging from said edge between said second endof the second plate and the fourth lug. The lugs of each counter-fittingelement extend via individual cut-outs provided in the closed frame.

This configuration of the fitting elements allows the lateral wings ofthe central fitting element and the lateral wings of the counter-fittingelements to be arranged in positions so that they are respectivelyfacing each other and separated by a distance corresponding to thethickness of the frame, in such a way that the first lug of the centralfitting element makes contact with at least the outer surface of thethird lug of the first counter-fitting element, and the second lug ofthe central fitting element makes contact with at least the outersurface of the fourth lug of the second counter-fitting element, in sucha way that the openings are aligned with each other and with the openingfor housing the bolt. The first lug can also make contact with thesurface of the first plate and the second lug can also make contact withthe surface of the second plate. In turn, the third lug can also makecontact with the outer surface of the first lateral wall and the fourthlug can also make contact with the outer surface of the second lateralwall. Moreover, the first lug can be joined to at least the outersurface of the third lug and the second lug can be joined to at leastthe outer surface of the fourth lug.

In accordance with the invention, the central fitting element and thecounter-fitting elements can be manufactured from carbon fibrereinforced resin, which advantageously contributes to reducing theweight of the coupling system of the present invention.

In accordance with the invention, the closed frame can furthermorecomprise an additional cut-out via which emerges at least part of thelateral load fitting and/or the complementary lateral load fittingwhich, in this case, are coupled to each other by means of a swiveljoint.

The swivel coupling can be materialised by means of an embodiment inwhich each lateral load fitting comprises a forward fitting and a rearfitting. In this case, the forward fitting comprises a first part fixedto a first side of the closed frame and a first free lug with a firstpassage hole, while the rear fitting comprises a first part fixed to asecond side of the closed frame opposite to said first side and a secondfree lug with a second passage hole.

The first free lug of the forward fitting and the second free lugforming part of the rear fitting are in contact with each other andemerge via said additional cut-out in such a way that said passage holesare aligned with each other.

Moreover, in this embodiment, the complementary lateral load fittingcomprises a plate joined to the rear spar of the central box of theempennage, as well as at least two wings emerging orthogonally from theplate, separated from each other and provided with vertically alignedmouths.

These mouths are aligned with the passage holes of the lateral loadfitting when the lugs of the lateral load fitting are positioned betweenthe wings, the mouths and the passage holes, in such a way that avertical space is formed for housing a pin by means of which the lateralload fitting is linked to the complementary lateral load fitting. Inorder to allow the lateral load linked fitting not to interfere with therotation of the empennage, provision is made so that the distancebetween the wings is greater than the thickness of the free lugs of thelateral load fitting and that the passage holes have, at least in theaxial direction, extensions greater than the diameter of the pin, insuch a way that the lateral load fittings can operate as a swivel. Forthis, the distance between the wings, the extensions of the passageholes and the dimensions of the free lugs can be designed such that thewings and the free lugs do not make contact when the empennage rotatesbetween the negative maximum angle of incidence (−θ₁) and the positivemaximum angle of incidence (+θ₂) and that they remain positioned inparallel planes for a mean angle of incidence corresponding to half theangle of rotation between said negative maximum angle of incidence (−θ₁)and said positive maximum angle of incidence (+θ₂).

The lateral load fitting and/or the complementary lateral load fittingare normally metallic though they could also be manufactured from carbonfibre reinforced resin.

Via the rotary linked fittings, the vertical component of theaerodynamic and inertial loads that are produced in the empennage istransmitted to the fuselage, while by means of the lateral load linkedfitting or fittings the horizontal component, in other words, thelateral load, of the loads produced on the empennage is transmitted,also to the fuselage.

In this way, and especially when the rotary fittings and the lateralload linked fitting or fittings are coupled to the central section of aclosed frame especially enabled to withstand the loads of the empennage,a transmission of the loads to the fuselage is achieved and, therefore,a distribution of those loads which contributes to an efficient couplingof the large dihedral empennage to the tail fuselage of the aircraft, bymeans of an arrangement of elements of great simplicity which are inturn easy to fit and maintain.

BRIEF DESCRIPTION OF THE FIGURES

Described below are certain aspects and embodiments of the invention onthe basis of some figures in which

FIG. 1 is a schematic view in upper plan of the arrangement of aempennage linked to the tail fuselage of an aircraft according to anembodiment of the present inventive system where the arrow indicates thedirection of flight of the aircraft;

FIG. 2 is a rear schematic view of the arrangement of boxes of the tailfuselage to which the present invention is applied;

FIG. 3A is a schematic view of the tail of an aircraft containing anempennage provided with the rotary system of the present invention, inthe cruise position;

FIG. 3B shows the empennage of FIG. 3A with a negative maximum angle ofincidence, corresponding to a position in an ascent manoeuvre of theaircraft;

FIG. 3C shows the empennage of FIG. 3A with a positive maximum angle ofincidence, corresponding to a position in a descent manoeuvre of theaircraft;

FIG. 4 is a front schematic view of an embodiment of a lateral loadlinked fitting which can be used in accordance with the presentinvention;

FIG. 5 is a schematic view in rear perspective of the tail fuselage ofthe aircraft to which the structure of the empennage shown in FIGS. 1 to4 is linked;

FIG. 6 is a lateral schematic view of a central rotary fitting elementapplicable in the system of the present invention;

FIG. 7 is an upper plan view of the central rotary fitting element shownin FIG. 6;

FIG. 8 is a schematic view in cross-section (rotated 900 in theclockwise direction) of the rotary fitting element shown in FIG. 6 seenfrom the line A-A′ appearing in that figure;

FIG. 9 is a schematic view in lateral elevation of an embodiment of thefirst lateral counter-fitting element used together with the centralrotary fitting element shown in FIGS. 5 to 8;

FIG. 10 is a schematic view in upper plan of the counter-fitting elementshown in FIG. 9;

FIG. 11 is a schematic view in cross-section along the line B-B′(rotated 90° in the clockwise direction) appearing in FIG. 9;

FIG. 12 is a schematic view in lateral elevation of an embodiment of thesecond lateral counter-fitting element used together with the centralrotary fitting element shown in FIGS. 5 to 8;

FIG. 13 is a schematic view in upper plan of the second counter-fittingelement shown in FIG. 12;

FIG. 14 is a schematic view in cross-section along the line C-C′(rotated 90° in the clockwise direction) appearing in FIG. 12;

FIG. 15 is a lateral view of a rotary fitting composed of the centralfitting elements and the lateral counter-fitting shown in FIGS. 6-14;

FIG. 16 is a schematic view in cross-section along the line D-D′appearing in FIG. 15;

FIG. 17 is a schematic view in perspective of an embodiment of thelateral load linked fitting applicable in the system of the presentinvention where just one of the lateral load fittings is seen fitted inthe central section of the frame for a better understanding;

FIG. 18 is a more detailed schematic view in perspective of the lateralload fitting attached to the rear par of the central box of theempennage shown in FIG. 17;

FIG. 19 is a more detailed schematic view in perspective of the lateralload counter-fitting shown in FIG. 17 attached to the central section ofthe frame;

FIG. 20 is a schematic view in cross-section of the lateral load linkedfitting shown in FIG. 17;

FIG. 21 is a schematic view in perspective showing the position of theforward fitting in the frame;

FIG. 22 is a schematic view in perspective showing the position of therear fitting in the frame;

FIG. 23 is a schematic view in upper plan of the forward fittingappearing in FIG. 17;

FIG. 24 is a lateral schematic view of the forward fitting appearing inFIG. 17;

FIG. 25 is a schematic view in cross-section along the line E-E′appearing in FIG. 24;

FIG. 26 is a schematic view in upper plan of the rear fitting appearingin FIG. 17;

FIG. 27 is a lateral schematic view of the rear fitting appearing inFIG. 17;

FIG. 28 is a schematic view in cross-section along the line F-F′appearing in FIG. 27;

FIG. 29 is a schematic view in perspective showing the complementarylateral load fitting appearing in FIG. 19;

FIG. 30 is a schematic view in lower plan of the complementary lateralload fitting appearing in FIG. 19;

FIG. 31 is a schematic view in cross-section along the line G-G′ of theof the complementary lateral load fitting appearing in FIG. 19, fittedin the central box of the empennage;

Appearing in these figures are numerical references identifying thefollowing elements:

-   1 empennage-   1 a right lateral box-   1 b left lateral box-   1 c central box-   2 first linked fitting-   2 a first rotary fitting-   3 second linked fitting-   3 a second rotary fitting-   4 lateral load linked fitting-   4 a lateral load fitting mounted in the frame-   4 b complementary lateral load fitting mounted in the rear spar of    the central box-   5 horizontal linkage shaft-   6 tail fuselage-   7 central frame-   7 a cut-outs-   7 b additional cut-out-   7 c passage holes for fastening pins-   7 d passage drill-holes for fastening bolts-   8 upper frame-   9 lower frame-   10 rudder-   11 rear spar of central box-   12 central fitting element-   12 a central wall-   12 b first end-   12 c second end-   12 d first lug-   12 e first opening-   12 f second lateral wing-   12 g first lateral wing-   12 h fourth lateral wing-   12 i third lateral wing-   12 j second opening-   12 k second lug-   12 l interior channel of the central fitting-   12 m holes for fastening pins-   12 n first lateral wall-   12 o second lateral wall-   13 first counter-fitting element-   13 a first plate-   13 b first end-   13 c second end-   13 d third lug-   13 e third opening-   13 f sixth lateral wing-   13 g fifth lateral wing-   13 h drill-holes for fastening pins-   14 second counter-fitting element-   14 a second plate-   14 b first end-   14 c second end-   14 d fourth lug-   14 e fourth opening-   14 f eighth lateral wing-   14 g seventh lateral wing-   14 h drill-holes for fastening pins-   15 complementary lateral load fitting mounted in the rear spar of    the central box-   15 a complementary opening-   16 bolt-   19 forward fitting-   19 a first piece-   19 b first free lug-   19 c first passage hole-   19 d drill-holes for fastening pins-   20 rear fitting-   20 a first piece-   20 b second free lug-   20 c second passage hole-   20 d drill-holes for fastening pins-   21 a plates-   21 b wings-   21 c mouths-   21 d drill-holes for fastening pins-   22 pin-   23 fastening pins-   24 fastening bolts-   (−θ₁) negative maximum angle of incidence-   (+θ₂) positive maximum angle of incidence

EMBODIMENTS OF THE INVENTION

FIGS. 1 to 6 schematically illustrate an embodiment of the coupling of a

-   large dihedral empennage 1 to the tail fuselage 6 of an aircraft.

The empennage includes a right lateral box 1 a and a left lateral box 1b arranged in a dihedral angle in the tail fuselage 6 of the aircraft,with separate rudders 10 being coupled to these lateral boxes, alongwith a horizontal central box 1 c which joins the lateral boxes 1 a, 1b. Provided in the rear spar 11 of the central box 1 a are means oflinkage 2, 3, 4 by which the central box 1 c is horizontally linked to aclosed frame structure comprising a central frame 7, an upper frame 8and a lower frame 9 (see FIG. 6), in the tail fuselage 6, in such a waythat, as can be observed in FIGS. 3A, 3B and 3C, the empennage canrotate vertically on a horizontal linkage shaft 5 between a negativemaximum angle of incidence −θ₁ (corresponding to a position in an ascentmanoeuvre of the aircraft) and a positive maximum angle of incidence +θ₂(corresponding to a position in a descent manoeuvre of the aircraft) inresponse to the actuation of actuator means (not represented in thefigures) which are connected to the empennage 1 and to a structuralelement of the fuselage of the aircraft. It can therefore be observedthat the large dihedral empennage to which the coupling system of thepresent invention is applied acts as an elevator.

The means of linkage comprise a first linked fitting 2 provided in theproximity of the right box 1 a, a second linked fitting 3 provided inthe proximity of the left box 1 b, and also two lateral load linkedfittings 4, 4′ which prevent lateral displacements of the empennage 1and which are arranged in the central box 1 a between the linked rotaryfittings 2, 3.

The first linked fitting 2 comprises a first rotary fitting 2 a providedin the central section 7 of the closed frame 7, 8, 9 and is linked bymeans of a first bolt 16 (shown in FIG. 16) to a first complementaryrotary fitting 15 provided in the rear spar 11 of the central box 1 c ofthe empennage 1, while the second linked fitting comprises a secondrotary fitting 3 a provided in the central section 7 and is linked bymeans of a second bolt 16 to a second complementary rotary fitting 15also provided in the rear spar 11 of the empennage 1.

In turn, each lateral load linked fitting 4, 4′ comprises a lateral loadfitting 4 a, 4 a′ provided in the structure of the central frame 7,linked to a complementary lateral load fitting 4 b provided in the rearspar 11 of the empennage 1. The lateral load fittings 4 a, 4 a′, 4 b arelinked together in such a way that they permit the empennage 1 to rotatearound the horizontal shaft 5. The two lateral load linked fittings 4 a,4 a′ are schematically illustrated in FIG. 4. These fittings are alsopresent in the coupling system shown in FIG. 5, though, for greaterclarity, the second fitting 4 a′ has been omitted from this latterfigure.

FIGS. 6-8 show an embodiment of the rotary fittings 2, 3 in which eachrotary fitting 2 a, 3 a comprises a central fitting element 12, a firstcounter-fitting element 13 and a second counter-fitting element 14.

In accordance with this invention, the central fitting element 12 is anelongated body comprising a first lateral wall 12 n, a second lateralwall with a second lateral wall 12 o, and also a central wall 12 a whichjoins the lateral walls 12 n, 12 o in such a way that between thelateral walls 12 n, 12 o, an interior channel 12 l is defined.

The first lateral wall 12 n presents a free edge from which emerge afirst lug 12 d with a first opening 12 e, a first lateral wing 12 garranged between the first end 12 b of the central fitting element 12and the first lug 12 d, and a second lateral wing 12 f arranged betweenthe second end 12 c of the central fitting element 12 and the first lug12 d. The second lateral wall 12 o also has a free edge from whichemerge a second lug 12 k with a second opening 12 j, a third lateralwing 12 i arranged between the first end 12 b of the central fittingelement 12 and the second lug 12 k, and a fourth lateral wing 12 harranged between the second end 12 c of the central fitting element 12and the second lug 12 k. The lugs 12 d, 12 k are coplanar with thelateral wall 12 n, 12 o from which they respectively emerge, while thelateral wings 12 f, 12 g, 12 h, 12 i do so from the respective lateralwalls 12 n, 12 o in the opposite direction to the central wall 12 a.

The first counter-fitting element 13 comprises a first plate 13 a with afirst end 13 b and a second end 13 c between which an edge is definedfrom which extend a third lug 13 d with a third opening 13 e. The thirdlug 13 d is coplanar with the first plate 13 a. The counter-fittingfurthermore comprises a fifth lateral wing 13 g which emerges laterallyfrom the said edge between the first end 13 b and the third lug 13 d,and a sixth lateral wing 13 f which extends laterally from that edgebetween the second end 13 c of the first plate 13 a and the third lug 13d. The second counter-fitting element 14 comprises a second plate 14 awith a first end 14 b and a second end 14 c between which an edge isdefined from which extend a fourth lug 14 d with a fourth opening 14 e,said fourth lug 14 d being coplanar with the second plate 14 a andpresents a fourth opening 14 e. The second counter-fitting elementfurthermore comprises a seventh lateral wing 14 g which emergeslaterally from the edge of the second plate 14 a between its first end14 b and the fourth lug 14 d, and an eighth lateral wing 14 f whichextends laterally from its edge between the second end 14 c of thesecond plate 14 a and the fourth lug 14 d.

The lateral wings 12 f, 12 g, 12 h g, 12 i of the central fittingelement 12 and the lateral wings 13 f, 13 g, 14 f, 14 g of thecounter-fitting elements 13, 14 are arranged in positions so that theyare respectively facing each other and separated by a distancecorresponding to the thickness of the central section 7 of the frame, insuch a way that the openings 12 m found in the lateral wings 12 f, 12 g,12 h g, 12 i of the central fitting element 12 are in correspondencerespectively with the drill-holes 13 h made in the lateral wings 13 f,13 g of the first counter-fitting element 13 and the drill-holes 14 h inthe lateral wings 14 f, 14 g. Said holes and drill-holes are in turnpositioned in such a way together with the passage holes 7 c that theyrespectively form spaces for fastening pins 23 (see FIG. 15) whichpermit the central fitting element 12 to be fastened to thecounter-fitting elements 13, 14 so that the part of the central section7 of the frame that lies between the respectively facing lateral wingsof the central fitting element 12 and of the counter-fitting elements13, 14 remains trapped between them.

The first lug 12 d of the central fitting element 12 makes contact withat least the outer surface of the third lug 13 d of the firstcounter-fitting element 13, and the second lug 12 k in the centralfitting element 12 makes contact with at least the outer surface of thefourth lug 14 d in the second counter-fitting element 14. In this waythe openings 12 e, 12 j, 13 e, 14 e are aligned with each other and withthe opening 15 a for permitting the bolt 16 to be housed.

The central fitting element 12 is arranged in a first side of thecentral section 7 of the closed frame 7, 8, 9 while the counter-fittingelements 13, 14 are arranged in a second side of the closed frame 7, 8,9. In order to allow the assembly of these fitting elements 12, 13, 14,the central section 7 presents individual cut-outs 7 a, via which extendthe lugs 13 d, 14 d of each counter-fitting element 13, 14. In theembodiment shown, the first lug 12 d makes contact with the surface ofthe first plate 13 a, and the second lug 12 k makes contact with thesurface of the second plate 14 a, while the third lug 13 d also makescontact with the outer surface of the first lateral wall 12 n and thefourth lug 14k also makes contact with the outer surface of the secondlateral wall 12 o.

FIGS. 4 and 17 to 31 show aspects of an embodiment of lateral loadlinked fitting 4 mounted in the central section 7 of the closed frame,in which each lateral load fitting 4 a, 4 a′ and the complementarylateral load fitting 4 b are coupled together by a swivel coupling.Although FIGS. 17 to 31 show just one lateral load fitting 4 a and itsvarious elements, this second lateral load fitting 4 a′ and its elementsare entirely analogous to the fitting 4 a, and the arrangement of thesecond lateral load fitting 4 a′ can be appreciated in FIG. 4.

In the embodiment illustrated in FIGS. 17 to 31, the lateral loadfitting 4 a (and therefore also the second lateral load fitting)comprise a forward fitting 19 and a rear fitting 20.

The forward fitting 19 comprises a first part 19 a fixed to a first sideof the central section 7, and a first free lug 19 b with a first passagehole 19 c. In turn, the rear fitting 20 comprises a first part 20 afixed to a second side of the central section 7 opposite to the firstside and a second free lug 20 b with a second passage hole 20 c. Thefirst free lug 19 b of the forward fitting 19 and the second free lug 20b of the rear fitting 20 are in contact with each other and emerge viathe additional cut-out 7 b in the central section 7 in such a way thatthe passage holes 19 c, 20 c of these lugs 19 b, 20 b are aligned witheach other.

The complementary lateral load fitting 4 b comprises a plate 21 a joinedto the rear spar 11 of the central box 1 c of the empennage 1, and twowings 21 b emerging orthogonally at different heights of the plate 21 a,separated from each other and provided with a pair of mouths 21 c, 21c′. The mouths 21 c, 21 c′ are in positions such that the mouths 21 c ofone side of the complementary lateral load fitting 4 b are aligned withthe passage holes 19 c, 20 c of the first lateral load fitting 4 a whenthe lugs 19 b, 20 b of the lateral load fitting 4 a are positionedbetween the wings 21 b, in such a way that the mouths 21 c and passageholes 19 c, 20 c thereby form a first vertical space for housing a firstpin 22. In turn, the mouths 21 c′ of the other side of the complementarylateral load fitting 4 b are aligned with the passage holes 19 c′, 20 c′ of the second lateral load fitting 4 a′ when the lugs 19 b′, 20 b′ ofthe second lateral load fitting 4 a′ are positioned between the wings 21b, in such a way that the mouths 21 c′ and passage holes 19 c′, 20 c′form a second vertical space for housing a second pin 22′. The arraythus formed can be seen in particular in FIG. 4.

The complementary lateral load fitting 4 b is fixed to the rear spar 11of the central box 1 c by means of fastening pins 24 which penetrate viadrill-holes 21 d made in the rear plate 21 of the complementary lateralload fitting 4 b and via complementary holes (not shown in the figures)made in the wall of said rear spar 11.

The distance between the wings 21 b is greater than the thickness of thefree lugs 19 b, 20 b of the lateral load fitting 4 a and the passageholes 19 c, 20 c have, at least in the axial direction, extensionsgreater than the diameter of the pin 22, in such a way that said lateralload fittings have a swivel fitted in their housings which permits therotation of certain fittings with respect to others. Specifically, thedistance between the wings 21 b, the extensions of the passage holes 19c, 20 c and the dimensions of the free lugs 19 b, 20 b are designed insuch a way that the wings 21 b and the free lugs 19 b, 20 b do not makecontact when the empennage 1 rotates between the negative maximum angleof incidence −θ₁ and the positive maximum angle of incidence +θ₂ andthey remain positioned in parallel planes for a mean angle of incidenceθ_(m) corresponding to half the angle of rotation between said negativemaximum angle of incidence −θ₁ and said positive maximum angle ofincidence +θ₂.

Each of the forward fittings 19, 19′ is fastened to its correspondingrear fitting 20, 20′ by means of fastening bolts (not shown in thefigures) which traverse drill-holes 7 d in the central section of theframe and the facing drill-holes 19 d, 20 d, 19 d′, 20 d′ respectivelyprovided in the front fittings 19, 19′ and rear fittings 20, 20′, insuch a way that part of the central section 7 of the frame that liesbetween those fitting 19-20, 19′-20′ remains trapped between them.

The lateral load fitting 4 a, 4 a′, the complementary lateral loadfitting 4 b, the central fitting elements 12 and the counter-fittingelements 13, 14 that are shown in the figures can all be manufacturedfrom with carbon fibre reinforced resin.

1. Pivoting coupling system of a large dihedral empennage to the tailfuselage of an aircraft, in which the empennage (1) comprises a rightlateral box (1 a) and a left lateral box (1 b) arranged at a largedihedral angle in the tail fuselage (6) of the aircraft, wherein itcomprises a horizontal central box (1 c) joining the lateral boxes (1 a,1 b), and which comprises a rear spar (11); and means of linkage (2, 3,4) for horizontally linking the central box (1 c) to a frame structure(7, 8, 9) of the tail fuselage (6) of the aircraft, which allow theempennage (1) to rotate vertically about a horizontal linkage shaft (5)between a negative maximum angle of incidence (−θ₁) and a positivemaximum angle of incidence (+θ₂) in response to the actuation ofactuator means which are connected to the fuselage (1) and to astructural element of the fuselage of the aircraft.
 2. A rotary systemaccording to claim 1, wherein the frame structure (7, 8, 9) comprises aclosed frame (7, 8, 9), the means of linkage (2, 3, 4) comprises a firstlinked fitting (2) provided in the proximity of the right box (1 a),said first linked fitting (2) comprising a first rotary fitting (2 a)provided in the frame structure (7, 8, 9) and linked by means of a firstbolt (16) to a complementary first rotary fitting (15) provided in therear spar (11) of the empennage (1); a second linked fitting (3)provided in the proximity of said left box (1 b), said second linkedfitting (3) comprising a second rotary fitting (3 a) provided in theframe structure (7, 8, 9) linked by means of a second bolt (16) to acomplementary second rotary fitting (15) provided in the rear spar (11)of the empennage (1), and each of the complementary rotary fittings (15)in turn comprising at least one complementary opening (15 a) alignedwith at least one opening (12 e, 12 j, 13 e, 14 e) in one of the rotaryfittings (2 a, 3 a) in order to form a space in which the bolt (16) ishoused; a lateral load linked fitting (4) in order to prevent lateraldisplacements of the empennage (1), which is provided in the central box(1 a) between the linked fittings (2, 3) and which comprises two lateralload fittings (4 a, 4 a′) provided in the frame structure (7, 8, 9)linked to at least one complementary lateral load fitting (4 b) which isprovided in the rear spar (11) of the empennage (1), the lateral loadfittings (4 a, 4 b, 4 a′,4 b) being linked together such that theypermit the empennage (1) to rotate on the said horizontal shaft (5). 3.A rotary system according to claim 2, wherein each of the rotaryfittings (2 a, 3 a) comprises a first fitting element (12, 13) with atleast one lower anchoring point (12 f, 12 h, 13 f, 14 f) and at leastone upper anchoring point (12 g, 12 j, 13 g, 14 g) and at least two lugs(12 d, 12 k, 13 d, 14 d) between said anchoring points (12 f, 12 g, 12h, 12 i, 13 f, 13 g, 14 f, 14 g), each lug (12 d, 12 k, 13 d, 14 d)being traversed by an opening (12 e, 12 j, 13 e, 14 e).
 4. A rotarysystem according to claim 2, wherein each rotary fitting (2 a, 3 a)comprises a central fitting element (12), a first counter-fittingelement (13) and a second counter-fitting element (14); the centralfitting element (12) is an elongated body which comprises a first end(12 b) and a second end (12 c), a first lateral wall (12 n) with a freeedge from which emerge a first lug (12 d) with a first opening (12 e), afirst lateral wing (12 g) arranged between the first end (12 b) of thecentral fitting element (12) and the first lug (12 d), and a secondlateral wing (12 f) arranged between the second end (12 c) of thecentral fitting element (12) and the first lug (12 d), a second lateralwall (12 o) with a free edge from which emerge a second lug (12 k) witha second opening (12 j), a third lateral wing (12 i) arranged betweenthe first end (12 b) of the central fitting element (12) and the secondlug (12 k), and a fourth lateral wing (12 h) arranged between the secondend (12 c) of the central fitting element (12) and the second lug (12k), a central wall (12 a) joining the lateral walls (12 n, 12 o), eachof said lugs (12 d, 12 k) being coplanar with the lateral wall (12 n, 12o) from which it emerges and said lateral wings (12 f, 12 g, 12 h, 12 i)extending from the respective lateral walls (12 n, 12 o) in the oppositedirection to said central wall (12 a); the first counter-fitting element(13) comprises a first plate (13 a) with a first end (13 b) and a secondend (13 c) between which an edge is defined from which extend a thirdlug (13 d) with a third opening (13 e) coplanar with the first plate (13a), a fifth lateral wing (13 g) laterally emerging from said edgebetween said first end (13 b) and the third lug (13 d), and a sixthlateral wing (13 f) laterally emerging from said edge between saidsecond end (13 c) of the first plate (13 a) and the third lug (13 d);the second counter-fitting element (14) comprises a second plate (14 a)with a first end (14 b) and a second end (14 c), between which an edgeis defined from which extend a fourth lug (14 d) with a fourth opening(14 e) coplanar with the second plate (14 a) with a fourth opening (14e), a seventh lateral wing (14 g) laterally emerging from said edgebetween said first end (14 b) and the fourth lug (14 d), and an eighthlateral wing (14 f) laterally emerging from said edge between saidsecond end (14 c) of the second plate (14 a) and the fourth lug (14 d);the lateral wings (12 f, 12 g, 12 h, 12 i) of the central fittingelement (12) and the lateral wings (13 f, 13 g, 14 f, 14 g) of thecounter-fitting elements (13, 14) are arranged in positions so that theyare respectively facing each other and separated by a distancecorresponding to the thickness of the frame (7), the first lug (12 d) ofthe central fitting element (12) makes contact with at least the outersurface of the third lug (13 d) of the first counter-fitting element(13), and the second lug (12 k) in the central fitting element (12)makes contact with at least the outer surface of the fourth lug (14 d)in the second counter-fitting element (14), in such a way that theopenings (12 e, 12 j, 13 e, 14 e) are aligned with each other and withthe opening (15 a) for housing the bolt (16), the central fittingelement (12) is arranged on a first side of the closed frame (7, 8, 9)and the counter-fitting elements (13, 14) are arranged on a second sideof the closed frame (7, 8, 9); the closed frame (7, 8, 9) comprises eachcut-outs (7 a) via which the lugs (13 d, 14 d) of each counter-fittingelement (13,14) extend.
 5. A rotary system according to claim 4, whereinthe first lug (12 d) also makes contact with the surface of the firstplate (13 a) and the second lug (12 k) also makes contact with thesurface of the second plate (14 a).
 6. A rotary system according toclaim 4, wherein the third lug (13 d) also makes contact with the outersurface of the first lateral wall (12 n) and the fourth lug (14 k) alsomakes contact with the outer surface of the second lateral wall (12 o).7. A rotary system according to claim 4, wherein the central fittingelement (12) is made of carbon fibre reinforced resin.
 8. A rotarysystem according to claim 4, wherein the first lug (12 d) is joined toat least the outer surface of the third lug (13 d) and the second lug(12 k) is joined to at least the outer surface of the fourth lug (14 d).9. A rotary system according to claim 4, wherein the counter-fittingelements (13, 14) are made of carbon fibre reinforced resin.
 10. Arotary system according to claim 4, wherein the closed frame (7, 8, 9)furthermore comprises an additional cut-out (7 b); each lateral loadfitting (4 a, 4 a′) and the complementary lateral load fitting (4 b) arecoupled to each other by means of a swivel joint.
 11. A rotary systemaccording to claim 4, wherein each lateral load fitting (4 a, 4 a′)comprises a forward fitting (19, 19′) and a rear fitting (20), theforward fitting (19, 19′) comprises a first part (19 a) fixed to a firstside of the closed frame (7, 8, 9) and a first free lug (19 b, 19 b′)with a first passage hole (19 c, 19 c′), the rear fitting (20, 20′)comprises a first part (20 a, 20 a′) fixed to a second side of theclosed frame (7, 8, 9) opposite to said first side and a second free lug(20 bb, 20 b′) with a second passage hole (20 c, 20 c′); the first freelug (19 b, 19 b′) of the forward fitting (19, 19′) and the second freelug (20 b, 20 b′) of the rear fitting (20, 20′) are in contact with eachother and emerge via said additional cut-out (7 b) in such a way thatsaid passage holes (19 c, 20 c, 19 c′, 20 c′) are aligned with eachother; the complementary lateral load fitting (4 b) comprises a plate(21 a) joined to said rear spar (11) of the central box (1 c) of theempennage (1), and at least two wings (21 b, 21 b′) emergingorthogonally from the plate (21 a), separated from each other andprovided with vertically aligned mouths (21 c, 21 c′), the mouths (21 c,21 c′) in the wings (21 b, 21 b′) are aligned with the passage holes (19c, 20 c, 19 c′, 20 c′) when the lugs (19 b, 20 b, 19 b′, 20 b′) of thelateral load fitting (4 a, 4 a′) are positioned between the wings (21 b,21 b′), the mouths (21 c, 21 c′) and the passage holes (19 c, 20 c, 19c′, 20 c′) thereby forming a vertical space for housing a pin (22, 22′);the distance between the wings (21 b, 21 b′) is greater than thethickness of the free lugs (19 b, 20 b, 19 b′, 20 b′) of the lateralload fitting (4 a, 4 a′) and the passage holes (19 c, 20 c, 19 c′, 20c′) have, at least in the axial direction, extensions greater than thediameter of the pin (22, 22′), in such a way that said lateral loadfittings (4 a, 4 a′, 4 b, 4 b′) can operate as a swivel.
 12. A rotarysystem according to claim 2, wherein the closed frame (7, 8, 9)furthermore comprises an additional cut-out (7 b); each lateral loadfitting (4 a, 4 a′) and the complementary lateral load fitting (4 b) arecoupled to each other by means of a swivel joint.
 13. A rotary systemaccording to claim 12, wherein the lateral load fitting (4 a, 4 a′) ismade of carbon fibre reinforced resin.
 14. A rotary system according toclaim 12, wherein the complementary lateral load fitting (4 b) is madeof carbon fibre reinforced resin.
 15. A rotary system according to claim2, wherein each lateral load fitting (4 a, 4 a′) comprises a forwardfitting (19, 19′) and a rear fitting (20), the forward fitting (19, 19′)comprises a first part (19 a) fixed to a first side of the closed frame(7, 8, 9) and a first free lug (19 b, 19 b′) with a first passage hole(19 c, 19 c′), the rear fitting (20, 20′) comprises a first part (20 a,20 a′) fixed to a second side of the closed frame (7, 8, 9) opposite tosaid first side and a second free lug (20 b b, 20 b′) with a secondpassage hole (20 c, 20 c′); the first free lug (19 b, 19 b′) of theforward fitting (19, 19′) and the second free lug (20 b, 20 b′) of therear fitting (20, 20′) are in contact with each other and emerge viasaid additional cut-out (7 b) in such a way that said passage holes (19c, 20 c, 19 c′, 20 c′) are aligned with each other; the complementarylateral load fitting (4 b) comprises a plate (21 a) joined to said rearspar (11) of the central box (1 c) of the empennage (1), and at leasttwo wings (21 b, 21 b′) emerging orthogonally from the plate (21 a),separated from each other and provided with vertically aligned mouths(21 c, 21 c′), the mouths (21 c, 21 c′) in the wings (21 b, 21 b′) arealigned with the passage holes (19 c, 20 c, 19 c′, 20 c′) when the lugs(19 b, 20 b, 19 b′, 20 b′) of the lateral load fitting (4 a, 4 a′) arepositioned between the wings (21 b, 21 b′), the mouths (21 c, 21 c′) andthe passage holes (19 c, 20 c, 19 c′, 20 c′) thereby forming a verticalspace for housing a pin (22, 22′); the distance between the wings (21 b,21 b′) is greater than the thickness of the free lugs (19 b, 20 b, 19b′, 20 b′) of the lateral load fitting (4 a, 4 a′) and the passage holes(19 c, 20 c, 19 c′, 20 c′) have, at least in the axial direction,extensions greater than the diameter of the pin (22, 22′), in such a waythat said lateral load fittings (4 a, 4 a′, 4 b, 4 b′) can operate as aswivel.
 16. A rotary system according to claim 15, wherein said distancebetween the wings (21 b, 21 b′), said the extensions of the passageholes (19 c, 20 c, 19 c′, 20 c′) and said free lugs (19 b, 20 b, 19 b′,20 b′) are designed such that said wings (21 b, 21 b′) and said freelugs (19 b, 20 b, 19 b′, 20 b′) do not make contact when the empennage(1) rotates between the negative maximum angle of incidence (−θ₁) andthe positive maximum angle of incidence (+θ₂) and that they remainpositioned in parallel planes for a mean angle of incidencecorresponding to half the angle of rotation between said negativemaximum angle of incidence (−θ₁) and the positive maximum angle ofincidence (+θ₂).
 17. A rotary system according to claim 15, wherein thelateral load fitting (4 a, 4 a′) is made of carbon fibre reinforcedresin.
 18. A rotary system according to claim 15, wherein thecomplementary lateral load fitting (4 b) is made of carbon fibrereinforced resin.